我无法弄清楚输入是否为空

Question

So I made a program, which loops 2 questions from an array. What I want to happen here is to prompt if the user entered blank or empty, and also if the user inputs any other letter, number or symbol aside from a, b, and c. What's happening here is whenever I input a on the first question it also prints "That answer can't be blank" which it shouldn't since I entered a valid input.

for(int i = 0; i < question.length; i++){
    do{
        System.out.print(question[i].prompt + "\nAnswer: ");
        answer = s.nextLine();
        if(!answer.equalsIgnoreCase("a") &&
           !answer.equalsIgnoreCase("b") &&
           !answer.equalsIgnoreCase("c")){  
                System.out.println("Invalid input!\n");
        } if(!answer.isEmpty()){
            System.out.println("The answer can't be blank.\n");
        }
    } while(!answer.equalsIgnoreCase("a") &&
        !answer.equalsIgnoreCase("b") &&
        !answer.equalsIgnoreCase("c") &&
        !answer.isEmpty());
    if(answer.equalsIgnoreCase(question[i].answer)){
            score++;
    }
}

Answer 1

your code should look something like this...

for(int i = 0; i < question.length; i++){
    do{
        System.out.print(question[i].prompt + "\nAnswer: ");
        answer = s.nextLine();
        if(answer.isEmpty()){
            System.out.println("The answer can't be blank.\n");
        }else if(!answer.equalsIgnoreCase("a") &&
           !answer.equalsIgnoreCase("b") &&
           !answer.equalsIgnoreCase("c")){  
                System.out.println("Invalid input!\n");
        } 
    } while(!answer.equalsIgnoreCase("a") &&
        !answer.equalsIgnoreCase("b") &&
        !answer.equalsIgnoreCase("c") &&
        !answer.isEmpty());
    if(answer.equalsIgnoreCase(question[i].answer)){
            score++;
    }
}

What I have changed in the code: removed multiple ifs, instead used if-else, and removed ! from !answer.isEmpty() . Hoping this will help you :-)

happy coding